Light Therapy for Psoriasis

When you get right down to it, the sun is a critical component for most forms of life on the planet. Without sunlight, plants can’t make the food they need to grow and thrive. Without plants, the cycle of life comes grinding to a halt. In short, sunlight is a pillar to life on Earth, and when it comes to treating certain inflammatory conditions, such as psoriasis, light may also hold the key to healing.


Psoriasis is a common autoimmune disease that causes skin cells to proliferate too quickly. Over time, these excess cells build up in thick, red and scaly or ashy-looking patches, called plaques, which can be very itchy, painful and unsightly. Psoriasis plaques tend to accumulate around the elbows, knees, legs, scalp, lower back, face, palms and soles of the feet. If left untreated, symptoms may progress and plaques can develop virtually anywhere on the body. Other symptoms of psoriasis include:

  • Dry skin that cracks or bleeds.
  • Pain, itching or burning around the patches.
  • Pitted, thick, ridged, discolored or crumbly fingernails and toenails.
  • Swollen, painful and warm joints.

According to the National Psoriasis Foundation, more than 8 million Americans have psoriasis. Worldwide 125 million people, or 2 to 3 percent of the total population, have the disease. But not all cases of psoriasis are the same. There are several different types of psoriasis including:

  • Plaque psoriasis – considered the “classic” manifestation of psoriasis, this type accounts for about 80 to 90 percent of all cases. Depending on the location and severity of plaques, there can be some variation in its presentation, but most cases of plaque psoriasis feature large, scaly patches of dry, itchy, painful skin.
  • Guttate psoriasis – this second most common type accounts for some 10 percent of cases, and features tiny spots of psoriasis all over the body. It’s often triggered by a bacterial infection, such as strep, and tends to be more common in children.
  • Pustular psoriasis – this less common form of psoriasis features pus-filled blisters on top of red, painful patches of skin.
  • Erythrodermic psoriasis – this least common form of psoriasis manifests as a red, peeling, painful rash over the entire body and can be the most debilitating form of the disease.
  • Palmoplantar psoriasis – this form of psoriasis affects the hands and feet, causing itchiness, pain and peeling on the palms and soles.
  • Inverse psoriasis – this type features smooth, red patches of inflamed skin in folds of skin such as under the breasts, along the groin, behind the knees and in the armpits.
  • Scalp psoriasis – this type of plaque psoriasis affects primarily the scalp, leading in severe cases to thick, crusty plaques all over the scalp which may extend to the forhead and back of the neck.
  • Nail psoriasis – this type causes discoloration and abnormal nail growth in the fingernails and toenails.


For millennia, people have been trying to find better ways to clear up psoriasis, and currently, there are a range of powerful drugs on the market that have proven helpful. But one relatively low-tech treatment that’s actually been around for over 100 years may be just as effective as the fancy (and expensive) biologic drugs when used by the right patients. Light therapy uses controlled and directed beams of certain bandwidths of light to penetrate the plaques and reduce the inflammation, which helps the body clear the plaques.

People being treated for psoriasis with light therapy may recognize the equipment as being similar to that of a tanning booth. Dr. Joel M. Gelfand, professor of dermatology and epidemiology and director of the psoriasis and phototherapy treatment center at the University of Pennsylvania Perelman School of Medicine, says in many cases, patients will go to their dermatologist’s office three times a week and step into “a machine that encircles them with ultraviolet light bulbs.”

When these bulbs are turned on for the right length of time, they can cause big improvements in symptoms. This is because light therapy for psoriasis “down regulates the immunological response in the skin,” Gelfand says. This means that it slows the proliferation of cells and the inflammatory response in the skin.

In turn, this downregulation “decreases the inflammatory cascade” and can help restore the skin to a more normal state, says Dr. Jessica Kaffenberger, assistant professor of dermatology with The Ohio State University Wexner Medical Center in Columbus. “That’s why it helps any inflammatory process,” and it doesn’t just help with psoriasis. In fact, light therapy is sometimes used to treat:

  • Contact dermatitis, a red itchy rash caused by direct contact with an allergen.
  • Eczema, a condition that causes patches of skin to become rough and inflamed, bleed or blister.
  • Tuberculosis of the skin, a bacterial infection.
  • Cutaneous lymphoma, a form of lymphoma that begins in the skin.
  • Severe acne.
  • Vitiligo, a disorder that destroys the skin’s pigment resulting in white patches.


The NPF reports that there are several different types of light therapy, each with their own specific pros and cons. Types of phototherapy include:

  • Ultraviolet-B light. This is the most widely used type of light therapy for psoriasis, directing UVB light to penetrate the skin cells in plaques and turn off the over production of the inflammatory skin response that results in psoriasis plaques. This approach typically uses a “narrow band of wavelengths between 311 and 312 nanometers” of UVB light, and is considered safe and effective for the treatment of plaque and guttate psoriasis, Kaffenberger says.
  • Sunlight. Many people with psoriasis report an improvement of symptoms in the summer months, when their exposure to natural sunlight tends to increase, and some dermatologists recommend that if you’re dealing with psoriasis, you should seek to get some natural sunlight every day. “Start with five to 10 minutes of noontime sun daily,” the NPF reports and “gradually increase exposure time by 30 seconds if the skin tolerates it.” It’s important to wear sunscreen on skin that is unaffected by psoriasis so that you don’t burn and don’t increase your risk of skin cancer. And don’t overdo it. Any amount of sunburn can be painful and potentially dangerous.
  • Psoralen and UVA (PUVA). This form of light therapy uses a combination of psoralen and long-wave ultraviolet radiation. Psoralen is an oral medication that primes the skin to the effects of ultraviolet light and allows the UVA bands to better penetrate the plaques.
  • Laser treatments. Excimer lasers deliver a specific wavelength of ultraviolet-B light (308 nanometers) via a handheld wand to pinpointed locations on the skin. This form of light treatment may cause less damage to surrounding skin because it can be focused directly on plaques, and it can be delivered in higher doses, which may translate to fewer sessions for some patients.

Most dermatologists warn against using tanning beds or sun lamps to try to treat the condition on your own and the NPF “does not support the use of indoor tanning beds as a substitute for phototherapy performed with a prescription and under the supervision of a physician. Only medical professionals should provide and advertise light therapy for the treatment of psoriasis.” One reason why is because commercially available tanning beds and sunlamps emit more UVA light than UVB, which may be more likely to burn the skin, speed aging and elevate risk for cancer. UVA light is also less effective than UVB, unless it’s being used in combination with a compound called psoralen as part of a PUVA treatment. Using psoralen in combination with a tanning bed is not recommended, “as it may result in severe sunburn,” the NPF reports.


Kaffenberger says that in her experience treating patients with moderate psoriasis, “at least 75 percent of patients improve with light therapy.” While it may not result in entirely clear skin in all cases, she says it’s a safe and effective way of making a marked improvement in most cases.

Gelfand agrees that light therapy can be highly effective, and may rival systemic biologic drugs in terms of skin clearance for some patients. “Randomized control trials have shown that approximately 70 percent of patients will get clear or almost clear of their psoriasis on phototherapy.” In a 2012 study he conducted, Gelfand compared phototherapy to autoimmune and biologic medications in 713 people with moderate to severe plaque psoriasis and found that patients receiving phototherapy had virtually the same results in terms of skin clearance as patients taking methotrexate, a common autoimmune medication that can cause difficult side effects for some patients.

More recent research has also shown phototherapy to be cost effective and helpful for many people. “We published an article in the cardiology literature about a year ago where we were trying to understand the impact of cardiovascular disease in people with psoriasis. And phototherapy is one of our comparators,” Gelfand says. “What’s interesting about the study was that people randomized to Humira (adalimumab) had fairly similar improvements in their psoriasis as people who got phototherapy. Humira is a fancy biologic that costs thousands of dollars per year, and it gives you some perspective when weighing (whether to use) a biologic, if phototherapy has similar efficacy.”

In some cases, a combination of biologics and phototherapy can lead to excellent results. Although light therapy is not a cure for psoriasis (it can’t alter the underlying autoimmune problem that triggers the overproduction of skin cells), it can send symptoms into remission and leave your skin much clearer after a period of treatment.


Because light therapy doesn’t involve any kind of surgical procedure or ingesting medications, it’s considered very safe with few side effects. “Light therapy can be a good option for pregnant women,” who can’t take systemic treatments, such as methotrexate or biologic medications, Kaffenberger says. This is because some of the systemic treatments can cause serious side effects that could harm the fetus. But with light therapy, the side effects are fewer and limited to the skin.

But there are some drawbacks. Gelfand says light therapy tends to work best on guttate and plaque psoriasis, but it doesn’t usually help much when dealing with psoriasis lesions on certain parts of the body, and it’s not the right answer for all patients. “It doesn’t work well in the scalp because it’s covered by hair,” making it difficult for the light rays to penetrate. And if you have psoriasis in the genital area, that can be a tricky area to treat. “You have to protect the genitals because they’re sensitive to burns and skin cancers,” Gelfand says. Therefore, “the ideal candidate is someone who has plaque or guttate psoriasis on the arms, legs and trunk.” Kaffenberger adds that “in some patients, it can actually worsen psoriasis,” and there’s no easy way to discern ahead of time who will see a worsening of symptoms or an improvement.

In addition, burning of the skin can be a problem. These burns are similar to any sunburn you might get after spending too long outside without protection. “If you’re not careful with the intensity of the light each time, as well as the amount of time – if that’s increased too rapidly – patients can burn,” Kaffenberger says. But because light therapy is typically administered in the doctor’s office in a controlled environment, that risk can usually be mitigated.

Gelfand says that an increased risk of skin cancer could also be a potential side effect of light therapy treatment for psoriasis, and while “I don’t want to diminish the theoretical concerns about cancer and aging of the skin,” those risks seem to balance out with the vast improvement in symptoms that many patients experience with light therapy. Also, because psoriasis features chronic inflammation – which has been associated with a higher risk of certain kinds of cancers – and the fact that smoking can contribute to both the development of psoriasis and cancer, “there are a lot of different factors at play here,” so it’s difficult to say for sure whether skin cancer risk is increased when using light therapy to treat psoriasis. “The biggest concern is burning, so we dose it pretty carefully,” he says.

That said, having to turn up at a doctor’s office multiple times a week for treatment is an inconvenience that can interfere with some patient’s use of the therapy. Though some at-home treatment devices exist, it’s not entirely clear yet whether they’re as safe and effective as in-office treatments. But Gelfand and his team are investigating that very question with a pragmatic trial that’s just begun enrolling participants. The study will compare the real-world effectiveness of at-home treatments to in-office light therapy in more than 1,000 people over about three years. The resulting data should help providers, patients and insurers better understand whether in-home phototherapy for psoriasis is as effective as in-office treatments.


Although many patients begin their search for help with psoriasis with a primary care physician, light therapy is typically administered by a dermatologist who specializes in phototherapy treatment for psoriasis.

No matter whom you visit first, it’s important to seek help for psoriasis because if it’s left untreated, symptoms can worsen and cause problems well beyond the skin, such as psoriatic arthritis, an inflammatory form of arthritis that develops in about 30 percent of people with psoriasis. “The biggest thing is to make sure that you see the doctor and get a diagnosis. Psoriasis can be debilitating,” Kaffenberger says.